This invention relates to novel and improved methods for selectively metallizing bodies and to the products which result from such methods.
More particularly, the present invention relates to imposing, by thermal or radiant energy, real images comprising non-conductive metallic areas on the surfaces of such bodies. Such images are then made clearer and built up with deposits of electroless metal.
Although applicable whenever it is desired to apply a metallic coating to a substrate, as for example, for decorative or protective effects, or to make electrical conductors of a wide variety of shapes and configurations, the procedures for metallization herein are particularly useful for making real images on a variety of base materials, e.g., resinous insulating laminated bases or porous non-conductive materials, e.g., cloth, fiberglass, paper, cardboard, ceramics and the like.
It is a primary object of this invention to provide a process to produce real images on substrates, which can be built up by electroless plating and, optionally, subsequent electroplated metal deposition.
Another principal object of this invention is to provide improvements in metallization processes in which a base is selectively sensitized to metallization by electroless plating.
An additional object of this invention is to provide base materials and processes for selective electroless metallization in which there are employed non-noble metal sensitizers which are much more economical in cost, but equivalent in performance to the noble metal-containing sensitizers used until now.
Another object of this invention is to provide adherent electroless metal coatings bonded in selected areas to base materials.
The desired selectivity can be obtained according to this invention either by treating predetermined areas of the substrate by well-known techniques such as printing, free-hand drawing, lithographing, silk screening, embossing with textile rollers, and the like, or by treating the entire surface and selectively exposing predetermined areas through a mask, through negatives, with heated dies, and the like.
It has now been discovered that an electroless metal deposit can be selectively and adherently applied to a substrate. The method uses a real image in selected areas on the surface, the image being catalytic to the build up of a metal layer thereon by electroless metal deposition. The real image comprises a non-conductive layer of metal nuclei. Although the process can produce real images or prints of any kind, its selectivity facilitates the production of current conductor lines, plates or terminals, as in the manufacture of printed circuits and contributes to the decorative or design process, as in the manufacture of name plates dials and other metallized plastics. In all cases, when following the teachings herein, there are obtained outstanding, unexpectedly high bond strengths between the electroless metal and the base, as well as excellent resolution of the image formed.